1. Field of the Invention
This invention relates broadly to the field of devices for controllably squeezing out the plastic contents from squeeze tubes in which they may be contained, but has particular application to those tubes of plastic building type compounds which are utilized in the construction and vehicle manufacturing industries for caulking, filling, adhering and other purposes.
2. Description of the Prior Art
Controllably dispensing the contents of squeeze tubes has represented a challenge to inventors ever since the first of such tubes were commercially presented to the public. In the early days, since such tubes principally contained toothpaste or cosmetic creams, the devices which were created usually involved some single mechanical means for rolling up the end of the tube or providing some vice-type compression. For such domestic and non-industrial uses, obviously one would not consider providing any type of air or gas compression squeezing means.
In the aircraft and building fields, however, for quite a number of years plastic caulking compounds, such as those of polysulfide, have been packed in cylindrical containers from one end of which the material is extruded when the other end is subjected to a compressed air or gas force applied to some type of plunger which can move axially down the cylindrical container. An example of such a device is that described and illustrated in U.S. Pat. No. 2,838,210 granted to Detrie, et al., on Dec. 21, 1954.
One difficulty with such prior art devices, however, is that the plastic material to be dispensed must first be packed in a cartridge which fits the particular gun-like compressed air device. Where large amounts of the material are to be dispensed and on a regular basis, the use of such a device can be well justified. However, where only small amounts are to be dispensed from time to time--particularly out "in the field"-- the use of large cartridges of material which fit into air gun devices presents a number of problems:
One of such problems is that the gun devices with their gas tanks and cartridges may be somewhat bulky and inconvenient to carry around. Another problem is that once the cartridge has been partly used, the remaining material may tend to "set up" in the cartridge unless used fairly soon thereafter. Still another problem with prior art devices is that the valving means have been wasteful of the compressed gas in that each time the trigger is pulled and released, there has been a momentary passage of the compressed gas from the bottle or other pressure container source through the valve to the atmosphere. Such wastage of the compressed gas can materially cut the operational time of a dispenser which is operated by gas from a small portable gas bottle in the field.
For some time, caulking compounds have been sold in squeeze tubes and these are quite useful for small and selective applications. Usually, with such tubes, there is provided both (i) a closure cap, which may be screwed onto the discharging end of the tube to completely cap the same and thereby prevent a setting up of the contained compound between periods of partial use thereof; and (ii) a conical dispensing nozzle which is substituted for the closure cap when it is desired to extrude any of the compound from the tube. However, heretofore, no one has devised any type of dispenser in which gas under pressure can be utilized controllably to extrude plastic material from a squeeze tube using the tube's own plastic nozzle, and where, upon completion of partial extrusion from the tube, the latter may be removed from the actual compressed gas dispenser and reclosed with its cap. In such devices, as have been developed to dispense the contents of squeeze tubes by the application of gas under pressure, the dispensing end of the tube has been inserted into a nozzle which is a part of the dispenser housing. Consequently, with each use, such housing nozzle becomes blocked by the tacky polysulfide or silicone caulking compound and must be immediately cleaned following each use. This can prove to be quite onerous-- particularly in field uses of these devices.